The Significance of Right‐Sided Precordial ECG Leads (V3R and V4R) in Assessing Right Ventricular Dysfunction: A Single Center Cross‐Sectional Study

ABSTRACT Background Right ventricular systolic dysfunction is associated with poor prognosis and increased mortality rates. Our objective was to investigate ECG changes in patients with this condition, focusing on the right‐sided precordial leads. Methods In this cross‐sectional study, 60 patients with right ventricular dysfunction were included from April 2020 to April 2021. Cardiac structure and function were assessed using 2D transthoracic echocardiography. Standard 12‐lead electrocardiograms and right‐sided precordial ECGs (V3R‐V4R) were obtained and analyzed for QRS complex configuration, ST‐segment elevation, and T‐wave morphology. Results In our study, the majority were male (70.0%) with a mean age of 58.76 years. The most common initial diagnoses were pulmonary thromboembolism (43.3%), chronic obstructive pulmonary disease (26.7%), and pulmonary hypertension (25.0%). The predominant ECG finding in the right‐sided precordial leads (V3R, V4R) was a deep negative T wave (90.0%). Patients with severe right ventricular systolic dysfunction often exhibited a qR pattern (41.2%), whereas those with nonsevere dysfunction showed rS and QS patterns (55.8%). Approximately 41.0% of severe RV dysfunction cases had ST segment depression in the right‐sided precordial leads, and 28.0% of patients displayed signs of right atrial abnormality. Conclusion The study found that qR, rS, and QS patterns were more prevalent in V3R and V4R leads among patients with severe and nonsevere right ventricular systolic dysfunction. The most common ECG feature observed was deep T‐wave inversion in these leads. The study recommends using right‐sided precordial leads in all patients with RV systolic dysfunction for early detection and risk stratification.

Right ventricular failure occurs when the right ventricle (RV) is unable to maintain sufficient cardiac output despite adequate preload (1).This dysfunction can be caused by increased RV afterload, decreased RV contractility, or a combination of both factors.Critically ill patients often experience RV failure, particularly because of conditions such as pulmonary embolism, pulmonary arterial hypertension (PAH), acute respiratory distress syndrome (ARDS), and sepsis (2).The presence of RV dysfunction is strongly associated with a poor prognosis and high rates of morbidity and mortality (Golpe et al. 2010).
In clinical practice, 2D transthoracic echocardiography (2D TTE) is commonly used to noninvasively evaluate RV dysfunction.However, ECG can also be a valuable tool for assessing a This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
patient's prognosis and guiding further diagnostic and therapeutic decisions.ECG offers advantages such as simplicity, widespread availability, and low cost, making it particularly useful in emergency triage situations (Vanni et al. 2009).While rightsided precordial ECG leads (V3R, V4R) have traditionally been used to detect right ventricular myocardial infarction (RVMI), there is currently no research on the ECG changes in these leads specifically in patients with RV dysfunction.
Therefore, the objective of this study is to investigate the ECG changes in the right-sided precordial leads (V3R, V4R) among patients with RV dysfunction.To the best of our knowledge, this is the first study to assess these ECG changes in this specific patient population.

| Setting and Design
This cross-sectional study was conducted at the Khorshid Hospital, which is affiliated with the Isfahan University of Medical Sciences (IUMS).This study aimed to evaluate patients with right ventricular (RV) dysfunction over 1 year.The evaluation period for this study was from April 3, 2020 to April 4, 2021.All eligible patients who were admitted to the hospital during this period with a diagnosis of RV systolic dysfunction were included in the study (convenience sampling).RV systolic dysfunction was confirmed by using 2D TTE based on the recommendations of the American Society of Echocardiography for cardiac chamber quantification in adults (Lang et al. 2015).Echocardiography was performed using standard views, with the patient in the left lateral decubitus position, using a Philips EPIQ 7 cardiovascular ultrasound machine.A single experienced examiner, who had completed a fellowship in echocardiography, obtained conventional echocardiographic images and cine loops of all patients using an M5S transducer.
Furthermore, a total of 60 sex-and age-matched controls with normal echocardiography were included for better comparison.

| Inclusion and Exclusion Criteria
The inclusion criteria for this study were as follows: patients aged 18 years or older with a confirmed diagnosis of RV systolic dysfunction, and patients who provided formal consent to participate and complete the study.RV systolic dysfunction was defined using 2D TTE based on the presence of one or more of the following criteria: tricuspid annular plane systolic excursion (TAPSE) <1.6 cm, basal RV free wall velocity (S′) <10 cm/s, or RV fractional area change (FAC) <0.35 (Jaff 2011;Lang et al. 2015;Rudski et al. 2010).Patients with a body mass index (BMI) of 18 or less, skeletal anomalies, such as pectus excavatum, and those with incomplete information were excluded from the study.A total of 60 eligible patients were selected to participate.

| Data Collection
Using a checklist, a general physician obtained the data.All completed questionnaires were thoroughly checked and verified for errors before the final analysis.Measurements of RV systolic function were taken, including TAPSE, RV fractional area change (FAC), and RV free wall velocity (S′).Left ventricular ejection fraction (LVEF), diastolic function, pulmonary artery pressure (PAP), pulmonary acceleration time, and right atrial (RA) size were also measured according to guidelines (Lang et al. 2015).
During the study, a standard 12-lead ECG and two right-sided precordial leads (V3R-V4R) were recorded from participants in a supine position at rest, with a paper speed of 25 mm/s and calibration of 1 mV/10 mm.The standard 12-lead ECG findings, including axis, rhythm, rate, P wave, PR interval, QRS width, and R-wave progression in precordial leads, were analyzed.Additionally, the findings from the two right-sided precordial leads (V3R, V4R) were examined, including P wave, QRS width, QRS pattern, QRS voltage, ST-segment, and T wave.If a patient exhibited serial ECG changes, all ECG patterns were analyzed.

| Statistical Analysis
Data were analyzed using descriptive statistics including mean ± standard deviation (SD), median, frequencies, and percentages wherever applicable.Differences between subgroups were assessed using a one-way analysis of variance (ANOVA) for continuous and normally distributed variables and a chisquare test (or Fisher's exact test) for categorical variables.A test was considered statistically significant if the probability value (p-value) was <0.05.All analyses were carried out using Stata software (version 14.1; Stata Corp, College Station, TX, USA).

| Ethics Statement
The study protocol (Ethics No. IR.MUI.MED.REC.1399.626)was approved by the Research Ethics Committee at Isfahan  ST depression was significantly more common in patients with severe RV systolic dysfunction than in those with nonsevere RV systolic dysfunction in right-sided precordial leads (V3R, V4R; 41.0% vs. 20.9%,p = 0.0001).Among the 60 patients with RV systolic dysfunction, deep T wave inversion was the most frequent ECG sign in right-sided precordial leads (V3R, V4R; 90%).These findings are summarized in Table 3.

| Discussion
This study showed qR pattern in V3R, V4R was significantly most common in patients with severe RV systolic dysfunction in    with RV systolic dysfunction showed inverted T-wave in the precordial leads.Negative T waves were closely associated with changes in RV systolic dysfunction.In other words, improvement in RV systolic dysfunction might be predicted by the disappearance of the negative T wave on precordial leads (Choi and Park 2012).
The mechanism responsible for the appearance of the negative T waves in precordial leads in patients with RV dysfunction may be associated with the development of rapid right ventricular pressure overload and enlargement (Ferrari et al. 1997;Kosuge et al. 2006;Yoshinaga et al. 1999).Some studies have attributed the mechanism of inverted T wave to myocardial ischemia, and the release of various chemical mediators such as catecholamines and histamine (Geibel et al. 2005;Meyer, Planquette, and Sanchez 2008;Sarin, Elmi, and Nassef 2005).
Early detection of high-risk patients with RV dysfunction by identifying inverted T waves in precordial leads on admission has significant therapeutic implications.Additionally, predicting the improvement of RV dysfunction by the disappearance of the inverted T wave is important, because persistent RV dysfunction is related to recurrent thromboembolic occurrences (Choi and Park 2012;Kim et al. 2009).Grifoni et al. (2006) found that persistent RV systolic dysfunction at hospital discharge occurred in nearly 20% of patients.Therefore, patients with persistent RV dysfunction at discharge should receive strict surveillance for recurrence.
Right axis deviation occurred in 35% of cases.The preexisting disease may also impact the axis deviation on presentation ECG.As we reported PTE was the most frequent diagnosis in patients with RV dysfunction (43.3%).Right axis deviation was described as the classic axis change associated with PTE (Nielsen et al. 1989;Panos et al. 1988;Sreeram et al. 1994).
This study showed that 28.3% of patients had right atrial abnormality and 5.0% of patients had left atrial abnormality.An increase in the P wave amplitude >2.5 mV, known as right atrial abnormality P wave, has been typically associated with RV dysfunction and PTE, consequently resulting from RV hypertrophy or enlargement and/or associated with acute obstruction from clot (Ullman et al. 2001).Previous studies indicated that right atrial abnormality has been reported in 2%-30% of PTE patients (Rodger et al. 2000;Weber and Phillips Jr 1966).
Our results illustrated that ST segment depression was a common finding on the right-sided precordial leads in our patients (26.7%), especially patients with severe RV systolic dysfunction.Furthermore, nearly 87.0% of patients were in normal sinus Rhythm.

| Limitations of the Study
Several limitations of this study can be addressed.First, the nature of the study design (cross-sectional) did not allow for further evaluation of any apparent associations over time.Second, our experience at a single hospital may not be applicable to the broader community.Last, the interpretation of the findings is constrained by the small sample size.Longitudinal studies with larger sample sizes are necessary to investigate the ECG findings of right-sided precordial leads in patients with RV dysfunction.

| Conclusion
This study revealed that the qR pattern, as well as the rS and QS patterns in V3R and V4R, was significantly more common in patients with severe and nonsevere RV systolic dysfunction, respectively (p = 0.0001).The most prevalent ECG feature observed was a deep negative T wave in the right precordial leads (V3R, V4R; 90.0%) in both groups.Therefore, it is recommended that right-sided precordial leads (V3R, V4R) be utilized in all patients with RV systolic dysfunction.This straightforward approach can aid in the early detection and risk stratification of patients presenting with RV systolic dysfunction.
Table4presents the right-sided precordial ECG leads, categorized by the initial diagnosis.A significant difference was observed in the frequency of right axis deviation among patients with COPD (62.4%),PTE (30.8%), and PH (6.6%; p = 0.033).The occurrence of right atrial abnormality was 43.8% in COPD patients, 11.5% in PTE patients, and 40.0% in PH patients, respectively (p = 0.001).ST depression in the right-sided precordial leads was notably more prevalent in COPD patients (43.8%) compared to those with PTE (19.2%) or PH (20.0%; p = 0.001).

FIGURE 2
FIGURE 2 | (A, C, and D) Show the qR pattern; and (B, E) demonstrate the rS pattern in V3R and V4R.Alternance of deep T wave inversion can be seen in B, D, and E. RBBB pattern is also notable in D.

TABLE 3 |
Assessing the standard 12 ECG leads and two right-sided precordial ECG leads based on the severity of RV dysfunction.
Kostrubiec et al. (2010) axis deviation; N, number; p, p value; RAD, right axis deviation.Ferrari et al. (1997)demonstrated that the precordial negative T wave was the most frequent ECG feature in acute pulmonary embolism patients with RV systolic dysfunction.Moreover, Zhan and colleagues reported that the most common ECG feature was T wave changes in RV systolic dysfunction patients (Zhong-qun et al. 2014).Kostrubiec et al. (2010)illustrated that all patients

TABLE 4 |
Assessing the standard 12 ECG leads, and 2 right-sided precordial ECG leads based on the first diagnosis.